Heat-insulating material and method for manufacturing same.



No Drawing.

- UNITED STATES P TENT- OFFICE.

CHARLES H. BELKN AP, OF NEW YORK, N. Y., ASSIGNOR TO ARMSTRONG CORKCOMPANY, 0F PITTSBURGH, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA.

HEAT-INSULATING MATERIAL AND METHOD FOR MANUFACTURING SAME.

To all whom it may concern:

Be it known that LCHAnLns H. BELKNAP,

. a citizen of the United States, and a resident of the borough ofBrooklyn, in the city and State of New York, whose post-ofiice addressis 42 Franklin street, New York city, New York, have invented certainnew and useful Improvements inI-Ieat Insulating Materials and Methodsfor Manufacturing the Same, of which the following is a specification.

My present invention relates to heat-insulating coverings for boilers,steampipes and the like, and is applicable to the manufacture of suchproducts for whatever urpose they may be designed. Commonly w 1enapplied .to machinery they are denominated .laggings, but when I usethat term in this specification I use it generically to cover alldevices having for their object the retention of heat, whether they arestrictly laggings or not; such, for example, as the linings ofrefrigerators, walls, partitions, etc., as well as boiler and pipecoverings.

It is well known that air wheniproperly confined is one of the best, ifnot the very best, of heat insulators, but it is essential that thereshould be no circulation; for a slight circulation, even through acontracted duct, results in considerable loss of efficiency.

It is therefore desirable to subdivide the space occupied by the lagginginto as many aircells havin no communication as is reasonably posslble.For this reason many forms of cellular'covering have been devised, whichanswera certain restricted utility. One of the best forms of the moresolid coverings is magnesia, made in shapes to fit the surfaces fromwhich heat would radiate; this has relatively low conductive power andalso includes a large amount of air space subdivided into exceedinglyminute cells. It is, however, costly and somewhat heavy. One of the bestkmds of material for these purposes iskieselguhr, called by many namesin the art, such as fossil meal,

fossil flour, diatomaceo-us, earth, silicious earth, diatomite, etc.Thissu'bstance consists of the exceedingly minute mineral skeletons ofinfinitesimally, small organisms called diatoms. Under the microscopethese little cellular skeletons are seen to be composed of immensenumbers of still more minute air-cells, each separated from its neighborby a thin earthy wall. In a mass which enables me 'to combine the kieselSpecification of Letters'latent. Patented Dec. 3, 1912. Applicationfiled April 29, 1908. Serial No. 429,860. a

Although innumerable attempts in-' employ it, it has heretofore beenfound impossible to solidify this material successfully, on account ofthe fact that all of the binding materials with which it has heretoforebeen attempted to come pound the kieselguhr fill up the spaces in thecells and expel a large part of the air, thus lowermg'its efliciency;and a. second and equally important objection has been that they renderthe finished product very heavy, greatly increasing the freight chargesand the gross weight of the machinery to which these articles have beenapplied; the low price of the various heat insulating materials rendersit of importance that'they should not be subjected to large freightcharges.

I have by experiment discovered a procelss I with other materials,into-a lagging w ich is of very superiorquality, of low cost, and smallweight. The new product or composition of matter consists of kieselguhr09111 .-bined. with or bound by lime, and also by preference mixed with.some porous or fibrous material, such as asbestos fiber; and

this new composition of matter, by' what-- ever process-it/fnay beproduced, I believe to be of my,"invention and aim to protect by myclaims. I have also devised what I I? believe to be an efiicient andnovel process for the production of the-product described, and certainof myclaims are addressed to this improvement in the art. I

To prepare the new composition of matter, or new'manufacture, I takediatomaceous earth in proportion ofabout seventyfive per cent; of fineground lime, such as lime hydrate, about twelve and a half per half percent.-; these are thoroughly mixed,

and either while mixing or afterward I add cent.;-of'asbestos fiber,about twelve and a to the mixture suflicient water tomake a,

paste'which will flow readily, say of abo t. i Paris. While in thiscondition I th r 1 I the consistency of moderately thin plaster ofcomposition into molds such as are m comf-j mon use in the art and whichdo not need I i description; the composition should run easily intothese molds, in which it is al- .lowed to remain until it is fully set.This setting is greatly facilitated by the application of a moderate andregular heat, such as that from live steam of about 125 lbs. pres- 5sure.

' molds upon suitable supports or otherwise in a closed chamber to whichthe steam may be admitted and in which-it may be maintained under thedesired pressure for so long as may be desired; no illustration of 'suchchambers is necessary, since they are common and well-known. In generalin about eighthours, depending on thesize and thickness of the articles,and the pressure .used, the material will be found to have setsufficiently to be removed from the molds, and at the end of that timeit is so removed and placed in any suitable drying apparatusp It may ofcourse be used while still damp, if desired, but it is weak and itsetliciency in this condition is low; until it is dried out, it is not inits best form.

The new article of manufacture may be handled in the same way as thewell-known magnesia laggings. It is readily cut, is sufliciently strongto withstand transportation easily, has a high efiiciency and is lighterthan any other lagging with which 301 am acquainted.

Another process, or more strictly a variation of the same process, is tomix the kieselguhr and asbestos with milk of lime which has beenpreviously prepared, and

is of such strength as to make with the admixture the rather thin mortarwhich is best for the filling of the molds with the least labor. So faras I am now advised, the'substances when thus united or mixed 40 form achemical combination, consisting of a mixture of calcium carbonate andcalcium hydrosilicate, which is much more strongly cohesive than personsskilled in the art would suppose. Whether theasbestos combines to anyextent with the other materials or whether it is merely embedded thereinI am at this time unable to say, nor is it material for the purposes ofmy invention. Whatever the theoretical explanation of the combinationmay be is for my purposes wholly unimportant; and whether the chemicalreactions are such as I have indicated orvary therefrom I neither knownor care.

By the words alkaline earth in my claims, I intend to cover either theearths themselves, such as calcium or magnesium or other oxids of salts.The alkaline earth used in the mixture may be in any of these forms. Forthe asbestos, I may upon occasion substitute mineral or organic materials of a sufficiently fibrous or pulverulent nature to serve thepurposes of the invention, such as spun glass or mineral wool,

etc. I believe, however, that the asbestos,

I therefore preferably arrange the ging is rendered somewhat porous,since after the material has setits shape and size do not substantiallychange in the process of drying, and the minute cellular spaces occupiedby the water are left vacant as it is dried out. I consider this anespc--' cially Valuable feature of the particular process which I havedevised for the manufacture of my improved "product. \Vhile the amountof water employed may be varied considerably in both directions, I findthe best results are obtained by the use of about 34; pounds of water toeach pound of dry material. This amount of water provides for the waterwhich is taken up in the indurating process, and leaves a surplussufficient to produce the cellular spaces above referred to, due to theformation of a portion of the water into steam.

Having thus described my invention, what I claim and wish to protect byLetters-Patent of the United States is:

' 1. As a new article of manufacture. heatinsulating material formedfroma mixture composed mainly of diatomite, an alkaline earth and water, aportion at least of the alkaline earth being combined with the diatomitein the form of a silicate, the material having, in addition to thecellular structure of its diatomite, a large number of air cells formedby evaporation of water contained in the mixture, substantially asdescribed.

2. As a new article of manufacture, a porous heat-insulating materialcomposed of diatomite, lime and a fibrousbinding material, a portion atleast of the lime being combined with the diatomitein the form of asilicate, the material being uncompressed and containing a large numberof artificial air cells in addition to the natural pores of thematerials used, substantially'as described. I

3. As anew article of manufacture, a porous heat-insulating materialcomposed of diatomite, lime and asbestos, a portion at least of the limebeing combined with the diatomite in the form of a silicate, thematerial being uncompressed and containing a large number of artificialair cells in addition to the natural pores of the materials used, andthe fibers of asbestos acting to bind or felt the materials together,substantially as described.

4. The herein described method of mak: ing heat-insulating material,which consists in mixing diatomite with not over thirty per cent. ofalkaline earth and with sulficient water to form a mixture which can bereadily poured, and shaping and indurating the mixture without anysubstantial compression thereof, some of the-excess water in the mixturebeing driven oif during the indurating, to thereby form a large numberof air cells within the mass, substantially as described. i

5. The herein described method of making heat-insulating material, whichconsists in mixing diatomite and a fibrous binding material with notover thirty per cent. of alkaline earth and with sufficient water toform a mixture which can be readily poured, and shapin and induratingthe mixture Without any su stantial compression thereof, some of theexcess water in the mixture being driven off during the induration, tothereby form a large number of air cells within the mass, substantiallyas described.

6. The herein described method of making heat-insulating material, whichconsists in mixing diatomite, lime and a fibrous binding material ,withsufficient water to make a relatively thin pourable mixture, shaping andsetting said mixture 'without substantial compression or shrinkage, andconverting some of the free water in the shaped article into steam anddriving the same ofi to thereby form a plurality of air cells throughoutthe mass, substantially as described.

cells due to convertin into steam during in uration, substantially 7.The herein described method of making heat-insulating material, whichconsists in mixing diatomite, lime and a fibrous binding material withsufficient water to make a relatively thin pourable mixture, shaping andsetting said mixture in an uncompressed-condition, and converting someof the water in the shaped article into steam and driving, the same ofito thereby form a plurality of air cells throughout the mass,substantially as described.

8. The method of making heat-insulating material, consisting in mixingdiatomite with not over thirty per cent. of an alkaline earth-and withfibrous material and water, molding the same, and indurating the wet'mixture in natural uncompressed condition in the mold to form asilicate combination between the diatomite and the alkaline earth whileforming a large number of small air the contained water as described. v

In witness whereof, I have hereunto set my name in the presence of twowitnesses.

- CHARLES H. BELKNAP.

Witnessesz' T. J. JOHNSTON, IRVING M. OBRIEGHT.

